1. Field of the Invention
The present invention relates to a temperature regulating apparatus, an exposure system including the temperature regulating apparatus, and a device manufacturing method using the exposure system.
2. Description of the Related Art
In recent years, it is demanded to attain both a high productivity and the formation of an ultrafine circuit pattern in the manufacture of devices such as semiconductor integrated circuit devices. To meet these demands, high-speed, high-accuracy alignment control is necessary. Alignment accuracy largely depends on the length measurement accuracy of a laser interferometer. To achieve an alignment accuracy on the order of nanometers, it is necessary to sufficiently suppress a fluctuation in the temperature of the interferometric optical path. For this reason, an exposure apparatus is supplied with a fluid, that is, a coolant, such as air or a liquid, whose temperature is regulated with high accuracy and which serves to suppress the influence of, for example, a change in the temperature of a clean room which accommodates the exposure apparatus and to remove heat generated in the exposure apparatus.
FIG. 10 is a block diagram showing the schematic arrangement of a conventional temperature regulating apparatus. A temperature detector 36 detects the temperature of air or a liquid serving as a fluid to regulate the temperature of an exposure apparatus. A compensation calculator 32 calculates the difference between a target temperature SP and the temperature detected by the temperature detector 36, and generates a manipulated value MV. A voltage detector 22 detects an AC voltage supplied from a commercial power supply 20. A voltage comparator 24 compares a reference voltage Vref and the voltage detected by the voltage detector 22, and generates a correction value Vcomp. A gain correcting unit 38 corrects the manipulated value MV, generated by the compensation calculator 32, based on the correction value Vcomp generated by the voltage comparator 24, and generates and supplies a manipulated value MVcomp to a power controller 28. The power controller 28 controls a power P, supplied to a heater 30, in accordance with the manipulated value MVcomp. With this operation, the temperature of the fluid supplied from the heater 30 to the exposure apparatus is regulated.
The power controller 28 includes, for example, a solid-state relay. The power controller 28 including a solid-state relay is energized to control the supply of an AC voltage to the heater 30 in accordance with the manipulated value MVcomp. The power consumption P of the heater 30 is given by:P=(Vrm2/R)×(T1/T0)  (1)where T0 is the prescribed period, T1 is the ON time of the heater 30, R is the resistance of the heater 30, and Vrm is the effective voltage of the AC voltage supplied from the commercial power supply 20.
Because the ON time T1 is controlled in accordance with the manipulated value MVcomp, the power consumption P of the heater 30 is controlled linearly with respect to the manipulated value MVcomp and, eventually, the manipulated value MV.
The correction value Vcomp generated by the voltage comparator 24 is given by:Vcomp=(Vref/Vps)2  (2)where Vps [V] is the AC voltage supplied from the commercial power supply 20, and MV [%] is the manipulated value generated by the compensation calculator 32.
Then, the manipulated value MVcomp calculated by the gain correcting unit 38 is given by:MVcomp=Vcomp×MV×10−2  (3)
In this manner, a fluctuation in the power supply voltage is corrected in accordance with the square value of the ratio between the reference voltage Vref and the AC voltage supplied from the commercial power supply 20.
When high-accuracy/high-resolution control is necessary, a thyristor can be used as the power controller 28. Phase control of the power controller 28, which uses a thyristor, has a voltage control mode in which the voltage is controlled in accordance with the manipulated value, and a current control mode in which the current is controlled in accordance with the manipulated value. There is also a method of temperature regulation using a DC power supply in place of an AC power supply.
In an arrangement, such as a temperature regulating apparatus including a thyristor that constitutes a power controller, which controls a voltage or current, supplied from a power controller to a heater, linearly with respect to a manipulated value generated by a compensation calculator, the output from the heater is nonlinear with respect to the manipulated value. In this case, stable, high-accuracy temperature regulation is difficult to perform.